Emails bouncing due to missing Message-ID header Print

Some older devices or third-party services (like scanners, legacy CRMs, or desktop bookkeeping software) that send email through your email account using SMTP might be getting rejected if the software is missing a Message-ID header.

What is a Message-ID?

A Message-ID is a unique identifier added to every email. It looks like this:

Message-ID: <20000101000000.1234567890@example.com>

This ID allows mail servers to track and thread emails properly, helping prevent abuse and spoofing.

Why Emails Without Message-IDs Get Blocked

Many email providers, especially Google/Gmail, now require this header as a basic form of identification. If it's missing, your message can be rejected outright or flagged as suspicious.

Most often, this issue comes from:

• Old software or devices (e.g., scanners) that send email but don’t generate a proper Message-ID
• Custom-coded applications that don’t build a full email header set
• Third-party apps using SMTP but skipping standard RFC headers

What You Can Do

1. Update your software or firmware
   Look for updates to your device or software. Modern versions typically handle headers properly.

2. Use an SMTP relay
   If you can't update the device, consider using an SMTP relay provider like SMTP2GO, Mailgun, or SendGrid. These services will often reformat headers to add a missing Message-ID automatically, among other things, reducing bounce risk. They often have a generous free tier. It's usually considered best practice to use an SMTP provider for sending transactional email rather than an actual mailbox, so this is our recommendation in any case. When using an SMTP relay, you will need to add DNS records to your domain name — the SMTP relay provider will advise what those are (e.g. a DKIM record) and supply the necessary records, which you can either pass on to Precedence (if we manage your DNS), or update yourself.

Other Delivery Notes

Note that correct mail headers are only one of many aspects of ensuring that mail servers accept your email. You should also ensure you have correct DMARC, SPF and DKIM records on your domain.

Not Sure?

If you are unsure if you are receiving bounces due to a missing Message-ID, forward your bounce message to our support team, and we'll investigate it for you.